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Message-ID: <20240904065908.1009086-5-svens@linux.ibm.com>
Date: Wed, 4 Sep 2024 08:58:58 +0200
From: Sven Schnelle <svens@...ux.ibm.com>
To: Steven Rostedt <rostedt@...dmis.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
bpf@...r.kernel.org
Subject: [PATCH 4/7] Add print_function_args()
Add a function to decode argument types with the help of BTF. Will
be used to display arguments in the function and function graph
tracer.
Signed-off-by: Sven Schnelle <svens@...ux.ibm.com>
---
kernel/trace/trace_output.c | 68 +++++++++++++++++++++++++++++++++++++
kernel/trace/trace_output.h | 9 +++++
2 files changed, 77 insertions(+)
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index d8b302d01083..70405c4cceb6 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -12,8 +12,11 @@
#include <linux/sched/clock.h>
#include <linux/sched/mm.h>
#include <linux/idr.h>
+#include <linux/btf.h>
+#include <linux/bpf.h>
#include "trace_output.h"
+#include "trace_btf.h"
/* must be a power of 2 */
#define EVENT_HASHSIZE 128
@@ -669,6 +672,71 @@ int trace_print_lat_context(struct trace_iterator *iter)
return !trace_seq_has_overflowed(s);
}
+#ifdef CONFIG_FUNCTION_TRACE_ARGS
+void print_function_args(struct trace_seq *s, struct ftrace_regs *fregs,
+ unsigned long func)
+{
+ const struct btf_param *param;
+ const struct btf_type *t;
+ const char *param_name;
+ char name[KSYM_NAME_LEN];
+ unsigned long arg;
+ struct btf *btf;
+ s32 tid, nr = 0;
+ int i;
+
+ trace_seq_printf(s, "(");
+
+ if (!ftrace_regs_has_args(fregs))
+ goto out;
+ if (lookup_symbol_name(func, name))
+ goto out;
+
+ btf = bpf_get_btf_vmlinux();
+ if (IS_ERR_OR_NULL(btf))
+ goto out;
+
+ t = btf_find_func_proto(name, &btf);
+ if (IS_ERR_OR_NULL(t))
+ goto out;
+
+ param = btf_get_func_param(t, &nr);
+ if (!param)
+ goto out_put;
+
+ for (i = 0; i < nr; i++) {
+ arg = ftrace_regs_get_argument(fregs, i);
+
+ param_name = btf_name_by_offset(btf, param[i].name_off);
+ if (param_name)
+ trace_seq_printf(s, "%s = ", param_name);
+ t = btf_type_skip_modifiers(btf, param[i].type, &tid);
+ if (!t)
+ continue;
+ switch (BTF_INFO_KIND(t->info)) {
+ case BTF_KIND_PTR:
+ trace_seq_printf(s, "0x%lx", arg);
+ break;
+ case BTF_KIND_INT:
+ trace_seq_printf(s, "%ld", arg);
+ break;
+ case BTF_KIND_ENUM:
+ trace_seq_printf(s, "%ld", arg);
+ break;
+ default:
+ trace_seq_printf(s, "0x%lx (%d)", arg, BTF_INFO_KIND(param[i].type));
+ break;
+ }
+ if (i < nr - 1)
+ trace_seq_printf(s, ", ");
+ }
+out_put:
+ btf_put(btf);
+out:
+ trace_seq_printf(s, ")");
+}
+#endif
+
/**
* ftrace_find_event - find a registered event
* @type: the type of event to look for
diff --git a/kernel/trace/trace_output.h b/kernel/trace/trace_output.h
index dca40f1f1da4..a21d8ce606f7 100644
--- a/kernel/trace/trace_output.h
+++ b/kernel/trace/trace_output.h
@@ -41,5 +41,14 @@ extern struct rw_semaphore trace_event_sem;
#define SEQ_PUT_HEX_FIELD(s, x) \
trace_seq_putmem_hex(s, &(x), sizeof(x))
+#ifdef CONFIG_FUNCTION_TRACE_ARGS
+void print_function_args(struct trace_seq *s, struct ftrace_regs *fregs,
+ unsigned long func);
+#else
+static inline void print_function_args(struct trace_seq *s, struct ftrace_regs *fregs,
+ unsigned long func) {
+ trace_seq_puts(s, "()");
+}
+#endif
#endif
--
2.43.0
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